There are many routes to attain a noble gas configuration as given below:
1. Attain configuration of noble gas helium (He) by losing all the four valence electrons one after the other. In this process, the net positive charge on the carbon atom increases during the loss of every electron. In such cases more energy is required to lose the next electron. This makes the task more difficult. Moreover, the C4+ cation ultimately formed in this process becomes unstable despite its noble gas configuration, because it has a small size with high net charge. Therefore, carbon atoms do not adapt this method to attain a noble gas configuration.
2. Now gas neon (Ne) in order to attain the stable configuration accept one by one the four electrons in the valence shell. In this method the net negative charge on the carbon atom increases while accepting every new electron. Hence, more energy is required for accepting the next electron by overcoming the increasing repulsive force making the task more and more difficult. Moreover, the C4- anion ultimately formed would be unstable in spite of its noble gas configuration, as it would have a small size with high net charge, making it difficult for the nuclear charge +6 to hold 10 electrons around it. For this reason, carbon atoms do not take this route to attain a noble gas configuration.
3. Now, take the case of Neon, where it shares four electrons of valence shell with four valence electrons of other atoms. This method enables two atoms to share valence electrons with each other. Valence shells of both the atoms overlap to accommodate the shared electrons, As a result, both the atoms attain a noble gas configuration without generating any net charge on them, essentially making the atoms electrically neutral. Because of these factors atoms attain stability. Therefore, carbon atoms adopt this route to attain a noble gas configuration.